Abrading apparatus



Feb. 15, 1938. WA. ROSENBERGER 2,108,210

ABRADING APPARATUS Filed Nov. 3, 1934 10 Sheets-Sheet l Feb. 15, 1938. w. A. ROSENBERGER 2,103,210 ABRADIVNG APISARATUS Filed Nov; 5, 1934 10 Sheets-Sheet 2 Feb. 15, 1938. V w. A. ROSENBERGER 2,108,210 I ABRADING APPARATUS Filed Nov. 3, 1954 10 Sheets-Sheet 5 MM Q WML 1 Fb. 15, 1938. I w. A. ROSENBERGER 2,103,210

ABRADING APPARATUS Filed Nov. 5, 1934 1o Sheeis-Slieer. 4

W/W/a/W 4. Rode/Merger Feb. 15, 1938.

w. A. ROSENBERGVER 2,108,210

ABRADING APPARATUS Filed Nov. 5, 1954 10 Sheet s-Sheer. 5

v JIM #WW 7 Feb. 15, 1938. w. A. ROSENIBERGER 7 2,103,210

ABRADING APPARATUS Filed Nov. 5, 1934 1o SheetsShee+- e 6 3 3 w. A. ROSENBERGER 2,108,210

ABRADING APPARATUS Filed Nov. 5, 1954 10 Sheets-Sheet 7 299 Mina/4% Feb. 15, 1938. w. A. ROSENBERGER I 2,108,210

ABRADING APPARATUS Filed Nov. 3, 1954 10 Sheets-Sheet 8 Feb. 15, 1938. w A, RQSENBERGER 2,108,210

ABRADI NG APPARATUS '///////II//////, '////////////A Jam 00W Patented Feb. 15, 1938 ABRADING APPARATUS William A. Rosenberger, Hagerstown, Md., assignor to Pan'gborn Corporation, Hagerstown, Md., a. corporation of Maryland Application November 3, 1934, Serial No. 751,364

31 Claims.

The present invention relates to abrading apparatus, and more particularly the present invention is concerned with apparatus for imparting a tumbling action to castings or other articles of work, and simultaneously abrading the surfaces thereof.

Apparatus of this general character has been heretofore proposed in which the work is disposed on an endless conveyer or in a rotatable drum, with the result that the castings or other articles of work are tumbled in avertical plane, Each piece of work asiit is tumbled accordingly describes a path that is located in a vertical plane, transversely disposed with respect to the direction of travel of the conveyer or drum, with the result that although each piece, in its travel, may rotate about a horizontal axis and thereby present a larger portion of its surface to the action of the abrasive, other portions thereof are only partially treated or else are not treated at all. This results in work that is imperfect, and

which must be either discarded or re-treated.

This disadvantage just described of the devices heretofore proposed is still more pronounced when the work handled by the apparatus takes the form of elongated articles, for the reason that such articles often remain in a horizontal position throughout the blasting operation, and the end portions of the work are not subjected to the 'action oi the abrasive This results in defective work. 1

Recently, because 'of improvements in abrasiveresistant materials and high speed bearings, it has become feasible to substitute for the earlier forms of air blast equipment, centrifugal blast devices of reasonable life, to direct the abrasive against the work in the tumbling mechanisms, thereby effecting material economies in the power required for the operation of such tumbling mech-' in such manner that the latter is improperly abraded, and also the tumbling mechanism fails to expose all of the work to the abrasive for equal periods of time, with the result that some of the articles of work are abraded to a greater extent than others. Moreover, such prior devices are found to possess dead'spots where the work short circuit or undergoes a tumbling action which is ineffective to bring it into range of the abrasive, and the work located in such spots is discharged from the machine in an uncleaned condition. Such work must accordingly be sorted out and returned to the apparatus for a second treatment, which entails delay and expense.

Although the centrifugal blast tumbling apparatus that have been heretofore proposed have been equipped with mechanism for reclaimingand abstracting large extraneous material from the abrasive and for feeding the abrasive back to the blast wheel, suchmechanisms not only fail to remove dust from the abrasive, with the result that large quantities of dust are fed to the wheel with the abrasive, reducing the abrading efllciencyof the mechanism, and is released into the atmosphere, unless a large capacity dust collector is coupled to the apparatus, which requires considerable power, but such mechanisms also fail to remove small fragments of castings and other extraneous materials from the abrasive, decreasing the effectiveness of the mechanism.

A more serious defect of the abrasive reclaiming mechanisms ofthe prior apparatus just described resides in the fact that they are incapable of feeding abrasive to the blast wheel in continuously sufficient quantities to keep the wheel operating at its full capacity, with the result that although such machines are capable of handling great quantities of abrasive, and should completely treat work in less time than nowrequired for air anisms. While combinations of centrifugal blastw equipment y re SO i d by their and tumbling mechanisms have been heretofore proposed, a serious defect inherent in the prior apparatus of this character'resides in the fact that the abrading mechanism has not been properly correlated with the tumbling mechanism. to efllciently abrade the work. In such prior mechanisms, articles of work are subjected to anonuniform abrading action, it being necessary to overblast and to underblast substantial parts of each-load to secure a fairly satisfactory blasting of the rest'of each. load. A Y v lt has also been. found that "centrifugal blast tumbling apparatus which have been heretofore proposed possess the further disadvantage of directing, an abrasive stream against-the work rasive reclaiming and feeding mechanisms that they do not even approach their potential operating efficiencies.

Such prior devices are also bulky and require.

considerable head-room.

It is accordingly the primary object of the present invention to devise an abrading apparatuswhich will efficiently present articles of work articles will be abraded to'a substantially greater extent than any other article.

It'is a further major object of this invention to devise an abrading apparatus which will cause a novel self-contained abrading apparatus having the individual work pieces to take paths that will cause all of the material contained in the apparatus to be progressively moved through the entire abrading zone, whereby all of the work is uniformly abraded.

It is another important object of the invention to devise an abrading apparatus which will tumble the individual pieces of work about vertical as well as horizontal axes, whereby the entire surface of each piece of work is uniformly abraded.

It is a still further object of the present invention to devise an abrading apparatus having means for causing the work to travel in a path that is substantially normal to the direction of the abrasive stream, whereby a superior cleaning action is secured.

The present invention further aims to provide means for reclaiming and cleaning the spent abrasive and returning it'to the abrasive-projecting mechanism of the apparatus, which requires a minimum of head-room, and requires a minimum storage of abrasive while maintaining a continuous maximum supply of abrasive to the projecting device or centrifugal wheel. It is a'further object of this invention to devise an abrading device having a work tumbling mechanism and a novel centrifugal blasting mechanism for projecting abrasive against the work as it is tumbled.

It is another object of my invention to devise a centrifugal blast wheel having an abrasive reclaiming and claiming mechanism which will not'only efliciently claim the abrasive, but which will also continuously supply abrasive to the blast I to keep it operating at,

wheel in such quantities full capacity, without requiring the use of an excessive abrasive reserve supply.

It is another object of this invention to devise, for use with apparatus wherein an abradlng operation is carried forth in a cabinet or housing, means for treating spent abrasive withdrawn from said cabinet, with a predetermined volume of cabinet andatmospheric air, theratio of cabinet to atmospheric air being variable without changing the total volume of air.

Still another object of the invention is to: provide an abrading apparatus of the character .having anfabrasive projecting mechanism and a work? tumbling mechanism, with a novel means forproperly correlating their operations. My invention also aims'to devise, for usewith an abrasive projecting device, means for automatically controlling the feeding of abrasive .theretoin accordancwithcertain phases of its operation.

It is another object, of my invention to equip a work tumbling device with a certrifugal blast Wheel, and to so install the wheel that it will uniformly treat the work contained in the tumbling devicep I It is a further object of my invention to devise an abrading apparatus that will efliciently expose all surfaces of the work to an abrasive stream, even when the work assumes widely varying shapes, and yet which will not undercut or over-cut the work. I

My invention further aims to devise a novel power transmitting mechanismdor driving the units of abrading apparatus.

It is a. further'-object of the invention to devise a novel abrasive cleaning and reclaiming device for use with an abrading mechanism.

A i'urther object of this invention is' to proto devise a' novel centrifugal blasting device,

.which is particularly useful in connection with the present abrading apparatus, although it is not limited to such use.

. Another object of the invention is to generally refine more detailed but yet important features ofabrading devices... I

Further objects of the present invention will become apparent as the detailed description thereof proceeds in connection with the annexed drawings and from the appended claims. In the drawings: Figure 1 is a front elevational view of the tumbling and abrading apparatus of the present invention, certain parts having been broken away for clarity of illustration.

Figure 2 is. an elevational view of the apparatus shown in Figure 1, as seen from the right hand side of that figure.

Figure 3 is a top plan view of the apparatus shown in Figures 1 and 2. I

Figure 4 is a fragmentaryand diagrammatic view taken along a vertical centrally transverse plane-ofFigure 1, certain parts being omitted to simplify the illustration.

Figure 5 is a diagrammatic sectional view taken substantially on line 5,5 of Figure i with the omission of certain parts to facilitate the illustration.

\ Figure 6 is a sectional view taken substantially along line 6-45 of Figure 5. 1

Figure 6A is a detailed view showing a modifled form of the center-piece shown in Figure 6. Figure '7 is a sectional view taken substantially along line 1-7 of Figure 6.

Figure 8 is a sectional view taken on line 8-8 of Figure 6, certain of theparts being omitted for clarity of illustration.

Figure 9 is a sectional view taken substantially on line 9'9 of Figure 6.

Figure lll is a fragmental sectional view taken on line Ill-Ill of Figure 9.

Figure 11 is a fragmental view showing the manner of joining together the segments of the tumbling center-piece illustrated in Figure 9, and it is illustrated on an enlarged scale.

Figure 12 is a diagrammatic view showing the relation of the supporting and actuating means associated with the tumbling unit of the invention. r

Figure 13 is a view in elevation of the power unit forming a part of the present invention.

Figure 14- is -a top plan view, with the lid rcmoved, of the gear box forming a part of the power unit shown in Figure 13.

Figure 15 is a top plan view of the lid of the gear box-shown in Figure 14.

Figure 16 is a sectional view taken along line lB-IB of Figure 14.

Figure 17 is view in elevation, with parts broken away for facility of depiction, of one elevator unit forming a part of the improved tumbling and abrading device of the invention.

Figure 18 is a sectional view on an enlarged scale, taken substantially along line l8-IB of Figure 17.

Figure 19 is a fragmental elevational view of,

the elevatorshown in Figure 18, as seen when looking in at the left of i that figure.

certain parts being broken away to simplify the illustration.

Figure 21 is a. sectional view taken substantially along line 2i-2l of..Figure' 20.

Figure 22 is a fragmental elevational view as seen when looking at the right or Figure 20.

' to follow.

Figure 23 is a sectional fragmentary view of the metering valve forming a part of the device shown in Figure'2l.

Figure 24 is a sectional view taken substantially along line 2424 of Figure. 23.

Figure 25 is-a fragmental view partly in section and partly in elevation of the cylinder andcheck valve assembly forming a part of the actuating means for controlling the doors of the machine. a

Figure 26 is .a view in end elevation of an automatic solenoid which may be used to control the metering valve of the present invention, and is shown in open valve" position.

Figure 27 is a view of the device shown in Figure 26 as it appears when observed from the right-hand side of that figure, and is shown in closed valve" position.

Figure 28, is a, diagrammatic illustration of the electrical circuit employed for controlling operation of the present invention.

With continued reference to the drawings, wherein like reference characters have been employed to designate like parts throughput the several views, I 1,2, 3 and 6, a brief description of the general structure and functional interrelation of the major units comprising the present invention will be set forth as a preface tothe detailed description Supported upon a cabinet (A) serving as a combined housing and fra'me unit is a centrifugal wheel (B) designed to disharge a stream of abrasive upon castings or other work being agitated within a tumblingunit (C). Spent abrasive escaping from tumbling unit (C) is collected in a trough element (D) and carried by a helical conveyer (E) to one side of the cabinet (A) where it is lifted byaneelevator unit (F) to the top of the cabinet. Power to operate conveyer (E), elevator (F) and other elements of the machine is furnished by a power unit (G).

The abrasive is fed from the top of elevator (F) into a second helical conveyer (H) by which it is conveyed to the opposite side 01' the machine against, a 'counterecurrent of air, which washes theabrasive and carries dust and other foreign matter cgmmingled with the abrasive away through an exhaust [pipe (1)., From the end of the conveyer (H) the-abrasive is disicharged into a rotary screen unit (J) from which escape -"of the cleaned or reclaimed abrasive is made into a storage bin (K).

From the storage bin, clean abrasive is metered by-a suitable valve into the pit of an elevator unit (L) which raises the abrasive to a level slightly above the centrifugal wheel (B) and feeds the abrasive through a spout (M) into the hopper of centrifugal wheel (B) preparatory to a repetition of the cycle just described.

It will thus be seen that during operation of the machine abrasive is being constantly circulated through a complete cycle which includes supplying abrasive to the centrifugal wheel, discharging a blast therefrom onto the work, collecting the spent abrasive, purifying the abraand referring particularly to Figures housing section 2i adapted to inclose the tumbling unit (C), and two auxiliary sections 22 and 23 Yocated one on each side of main section 2| for a purpose to be hereinafter disclosed. The front and rear walls of the cabinet are'indicated at 24 and 26 respectively, the right hand and left hand side walls being shown at 25 and 21 respectively.

Located in front and rear cabinet walls 24 and 25 are doorways 28 adapted to be closed by front and rear door assemblies 29 and Bi respectively, and as the door frame and door for both front and rear closures are of similar construction, a detailed description of only the front door will be given.v The door frame preferably consists of two vertical side panels 32 joined toff'ront cabiriet wall 24 by angle members 33 and carrying at their forward edges further angle members 34, the front face of the latter angles being flush with the front edge of the' sidepanels, Secured to angles 34 (Figure 8) by suitable means as, for

I example, bolts 31, are two vertical strips 35 and 35 of unequal width and so disposed as to provide a channel 38 adapted to accommodate door 29 for reciprocation therein. The door frame at the top is closed by a panel 39. At its bottom, the door frame comprises a tilted slab 4i secured to a flange 42 formed on front cabinet wall 24.

The door proper comprises a fiat panel 43 having guide extensions, 44 adapted to slide within channels 38. The lower part of door panel 43, bent inwardly at 4 5, is provided on its inner surface with a rubber sealing flap 46 which folds around the bottom edge of the panel to form a tightly sealed fit against and flush with the upper edge of slab 4| when the door is in closed position.

, Provided on the exterior face of door panel 43 are two strengthening ribs 5| between which extends a cross-piece 52 providing a shoulder 55 to which is fastened by bolt 55, one end of a piston rod 54 which is operable to effect elevating and lowering movements of the door 29. The

other end of the piston rod is fastened to a piston (not shown) locatedwithin a cylinder 55 which is provided with heads 57 and 58 fastened together by the rods 59.

Reciprocation of the piston within cylinder 56 is effected by means of compressed air admitted to the cylinder through a pipe 6i and. controlled by a valve 52. Admission of air under compression to the lower end of the cylinder acts to cause upward displacement of the piston and elevation of door 28. Lowering of the door results upon actuation of valve 52 to vent pipe 6| to the atmosphere.

In order to cause door 29 to lower at first rapidly and then come to a gentle and gradual rest upon slab 4|, a specially designed check valve 53 is inserted in pipe line 6| between control valve 52 and cylinder 55. As seen in Figure 25, valve body 53 defines two chambers 64 and 65, connected by a small pa chambers 64 and 65 1s a' lar e Y-Pa s e 6 which adjacent chamber 54 forms a valve seat 58 for accommodating a ball check 69.

Also joining Threaded into the valve body and extending downwardly into the by-passage 61 is a bolt 1| provided with a locknut 12 and adapted to throttle flow of air contained in the machine.

through by-passage 61 by decreasing the cross sectional area thereof.

When the door 29 is being .lowered, it is observed that the pressure of air escaping from the cylinder into chamber 64 is initially comparatively large, and is effective to unseat ball .check 69. As a result of this operation egress of air through by-passage 61 as well as the restricted passage 66 is effected. The rate at which air escapes through by-passage 61 may be controlled readily by adjustment of throttle bolt ll and setting of locknut 12, the rate of initial lowering of door 29 in this manner being under control. As the door continues to lower and approaches its closed position, the pressure of air escaping from the cylinder into chamber 64 is lessened and ball 69 ultimately comes to rest upon its seat 58,

thereby prohibiting escape of air through bypassage 61. Since air may at this stage escape only through the narrow restricted passage 66, the piston can descend only very slowly, and the door is accordingly brought to a cushioned and gentle rest.

By the provision of a door opening and closure for both the front cabinet wall 24 and the rear cabinet Wall 25, it is possible to either load or unload the machine at both front and rear. This feature is of major importance. as it allows more rapid and facile loading and unloading of themachine, and greater ease of inspection of the work With reference now particularly to Figures 4, 6 and 9, the tumbling unit (C) is seen to comprise a pair of open ended drums' SI and 82 which are spaced apart and have their open ends facing each other. Drums 8| and 82 are mounted for rotation on a roller and shaft organization to be presently described. Mounted for rocking movement between the drums is a center-piece or segment 83 which prevents the work or other material from escaping from the drums, and also performs an important part of the "tumbling and discharging operations. Material is dumped into the'gap formed between drums 8| and 82 and the latter are rotated in the direction indicated to cause the work to tumble or cataract on itself while it is subjected to the action of the abrasive blast from centrifugal blast wheel (B). When it is desired to discharge the work, the direction of rotation of the drums is reversed or center-piece 83 is .the two drums and as the material strikes the sloping faces of member 83, it isidefiected axially toward drums 8| and 82. Drums 8| and 82 accordingly pick up the work and lift it through a certain angular distance and then, owing to the bowl-shaped configuration thereof, dump it towards the center of the device, and onto the top of the other material contained in the apparatus. It is accordingly seen, that in addition to imparting a circular tumbling action to the material in the apparatus, the drums BI and 82 also impart an axial movementthereto, which results in eiiiciently exposing all of the surfaces of the material to the abrasive or other cleaning materials directed between the drums. It has been found that when the work takes the form of elongated articles, such articles are tumbled so as to rotate about their axes and also about axes disposed transversely to their axes, with the result that their entire surface is presented to the blast.

When the treating operation just described has been completed, and it is desired to discharge the contents of the mill, it may be effected in two ways, depending upon whether it is desired to discharge the contents at the front or at the rear of the mill. If it is desired to discharge the material at the front of the apparatus the direction of rotation of drums 8| and 82 is reversed, as indicated by the dotted arrow in Figure 6 which causes. the material to be discharged over the front end of member 83, and if desired, a chute or conveyer or any other suitable means may be associated with the device for conveying the material away to bins or the like.

On the other hand, should it be desired to discharge the material at the rear side of the mill, drums BI and 82 may be allowed to continue to rotate in the direction of the arrow in Figured,

and member 83 brought into discharging position (Figure 4 as shown in dotted lines). Bringing member 83 into discharging position causes the normal tumbling rotation of drums 8| and 82 to convey the material over the rear end of .member 83. Member 83 may then be rocked back into the position illustrated in Figures 4 and 6, and the apparatus re-charged in the manner previously described.

With regard now to the path of travel taken by work within the tumbling unit, and to the exposure of said work to the blasting action of the abrasive stream, Figures 4 and 5 illustrate diagrammatically by arrows both the travel path taken by the work and the range of the blasting stream, solid line arrows indicating the travel path taken by the work units and dashed line arrows indicating the range of the blast stream.

By a comparison of the two figures, it will be seen that due to the bowl shaped inner contour of the drums 8| and 82, a dual motion is imparted to ,work therein disposed/the work being elevated from the bottom of the drum in an upward direction as seen in Figure 4, and at the same time being advanced toward the centerpiece 83 thus in effect describing aspiral path. Upon falling away from the drum and downward along the top of the work pile the individual units are deflected by the slopes of the center-piece back toward the drums, although articles of work may frequently migrate back and forth across the center-piece from one drum to the other. As seen in Figure 4, the work pile is indicated generally by a dot and dash line.

By the motion just described, each and every unit of work is moved within the tumbling unit through the complete range of strength of the abrasive blast, being subjected to both the mild abrading action of the stream fringe and the intensive action of the most concentrated central portion of the stream. In this manner the work is subjected to entirely uniform action; no part thereof being more or less exposed than any other part and the evil effects of undercutting and overcutting being entirely overcome.

Inasmuch as the abrasive in the present case is discharged through a solid angle and not in a. plane, and as work is passed laterally as well as forward and backward'through the blast of'abrasive, the possibility of uneven and localized abrading action such as occurs were the stream of abrasive discharged in substantially a plane sheet parallel to the axis about which the work is tumbled.

With reference now to Figures 6, 9 and 12, each illiary cabinets 22 and 23.

Preferably disposed between each pair of tracks 84 of .drums 8| and 82 are toothed portions 9 I, which are adapted to mesh with pinions 92 rigidly secured to rear shaft 81. Power may be applied to shaft 81 by power unit (G) in a mannerhereinafter disclosed.

Drums 8| and 82 are restrained against axial movement by means of thrust bearing assemblies of any desirable form. In the present instance they take the form of rollers 93 which are disposed between the outer tracks 84 and the toothed portions 9| of the drums, one roller being provided at the front and one at the rear of each drum. Rollers 93 are rotatably journalled upon base members 94 which are in turn secured to brackets 95, and the latter are secured to housing walls 25 and 21 employed to enclosethe apparatus.

Base members 94. are adjustably secured to brackets 95 by means of bolts 98 which are ac- 95. Lateral adjustment of base members 94 may I commodated within slots 91 provided in brackets be effected by loosening bolts 96, sliding the bolts within slots 91, and retightening the boltsin their new position. Furthermore base members 94 are provided at diagonal corners with lugs 98 and 99 which depend from the base and engage the edges of the brackets 95 to prevent rotation of base plates 94 with respect to brackets 95upon application of side thrust to rollers 93. It will be appreciated that the lug depending from the forward side of base 94 is located on the opposite side of the roller 93 from that which receives the drum side thrust. By this construction, shearing stresses on bolts 98 are materially lessened, as nearly all of the torsional forces applied to base plates 94 by the'drums are counteracted by the abutment of lugs 98 and 99 against the edges of the base plate.

Threaded into the end housing of roller 93 is a grease fitting IllI whichextends through an aperture in the front cabinet wall 24 and through a .rubber flap I82, held by guide members I83 illustrated for supporting and rotating the drum assemblies, it is to be understood that any other suitable means may be employed without affecting the essential characteristics of the invention. From the structure thus far developed it is evident that drums 8I and 82 are rotat'ably supported upon rollers,85 located below the drums and that rotation of the drums is effected by means of pinicns 92 acting in meshing engagement with gear tracks 9 I. It will be further evident that lateral or side shifting of the drums is obviated by means of thrust roller assemblies 93. Center segment 83 is of arcuate shape, and as seen in Figures 4 and 6, it is provided with. a front end I05 and a'rear end I86 which are preferably disposed approximately 180 apart. Member 83 is provided with a pair of downwardly inclined walls II", which function to cause the work to slide axially towards drums 8| and 82 when it is dumped into the barrels. These walls .tion when the barrels are rotated and the work is picked up thereby. As seen in Figures 4 and 6, member 83 is of uniform thickness throughout its entire length. However, the centerpiece may be made thicker at its front end than at its rear end, if desired, to facilitate loading and unloading, without departing from the spirit of the invention as shown 'at I28 of Figure 6A. 1

Member 83 is provided with a pair of spaced tracks I08 which rest upon rollers I09. -Rollers I 09 are fastened upon front and rear shafts H8 and III. Member 83 is adapted to be rocked through an angle of approximately 96 from the tumbling position shown in Figures 4 and 6, into the discharging position shown in dotted lines in Figure 4, by any suitable means, but I preferably provide a gear tooth portion I I2 on the outer surface of member 83, which meshes with a pinion I I 3 carried by front shaft I I8. Shafts I I and I II are.journalled in bearings II4 (Figure 2) provided adjacent bearings 88 on shelf 89. Power for producing rotation of shafts I III is supplied by power unit (G) in a manner to be hereinafter disclosed.

It will thus be readily apparent that centerpiece 83 is rotatably supported upon rollers I89, located below it, and it is adapted to be rotated by means of pinion II-3 meshing with gear rack II2. Lateral displacement or side play of the center-piece is prevented by means of flanges II5 formed on rollers I09 which engage the sides of roller tracks I88.

The drums are preferably provided with bowl shaped interiors II6 having depressions II1 into which are fastened cleats I I8. As seen in Figure 6, cleats II8 are provided with a beveled face II9 adaptedunder operating conditions to pick up and tumble the work, and a toothed face' I2I adapted under normal discharge conditions to engage and lift pieces of work to the level of the discharge door, when the machine is discharging from the front.

It will be noticed that beveled face II9 of the cleats is inclined slightly toward the center of the machine for the purpose of urging pieces of 'work elevated by the beveled face of the cleats toward its centerpiece, and to also impart a general axial motion as well as a circumferential motion to the pieces of work being tumbled in the drums. Such axial urging is augmented by the bowl shaped inner contour of the drums which also impart a side or axial motion to the work pieces being tumbled.

It will be further noted-with continued reference'to the cleats, that the edges I22 (Figure 9) of the teeth facing away from the center-piece are vertical in contrast to the inclined edges I23 facing toward the center-piece. Edges I22 of the cleat teeth are formed vertically or parallel to the drum edge in order that during normal discharging, pieces of work picked up and elevated toward the door by the cleats will be restrained against falling away from the cleats toward the center-piece before reaching the door level.

Thus'it will be evident that beveled face H9 and toothed face I2I perform opposite functions in engaging pieces of work; beveled face I I9 tending to urgev the pieces of work toward the centerpiece and toothed face I2I restraining the pieces of work against such motion.

As seen in Figures 6 and .9, the edges of I drums 8| and 82 adjacentthe' center-piece are provided with a continuous series of undulations I24 which provide lands I25 and grooves I28 along the periphery of the drums adjacent the center-piece. These undulations are effective to prevent lodgreplace only the segment subjected to excessive wear, instead of replacing the entire center-piece. Great savings and economy of operation and upkeep are the result of such construction. Each segment I28 is provided at its end with aflange I29, similar flanges of adjacent segments being locked. together by bolts I30. Formed at the outer end of flanges I29, and disposed normal thereto, are flanges I3I which mate with similar flanges I32 formed on gear track- .I I2 and secured to the latter 'by bolts I33. Thus it is seen, that when assembled, center-piece segments I28 and gear track I I 2 formv a rigid unit of great strength. Moreover, as track 2 is detachable from segments I28, and as it is not exposed to the abrading action, it may be secured to a replacement segment and be used over again.

With reference now to Figure 6 of the drawings, front door 29, as previously set forth, is shown in closed position. Secured to front door panel 43 on each side thereof and extending inwardly therefrom, is a bracket I4I provided at its lower and inner corner with a lug I42 extending toward the center of the door assembly. Hinged to each bracket MI by means of a pin I43 or the like, is an arm I44, said arms at their inner extremities being joined by a cross-bar I45.

Secured to cross-bar I45 is a segment I46 of a configuration similar to the segments of the center-piece and adapted to rest on the front end I I15 of the center-piece when the front door is in its closed position. I

It is observed that under normal conditions, when the front door is closed, arms I44 will rest upon lugs I42, at which time segment I46 will rest upon the front end of the center-piece.

However, in the event that the front end of the center-piece should be disposed slightly higher than its normal position, segment I46 may freely accommodate itself to such positions, as arms I44 will merely rise to a compensating position from an at rest position upon lugs I42.

Furthermore, shouldinadvertent rotation of the center-piece with attendant raising of the front end thereof be effected while the door is' in closed position, segment I46 will merely raise in response to the urge of the front end of the center-piece, and arms I44 and I45 will rotate together with segment I46 about axis I43 until segment I46 is brought to rest against door panel 43. Auxiliary segment I46 is thus automatically adjustable to any disposition ,of the center-piece when the -front door of the machine isclosed,

Auxiliary segment I46 is provided in order that, under normal tumbling and blasting conditions of operation, the effective extent of the centerpiece may be great enough to prevent inadvertent escape of work pieces or abrasive over the front end of the center-piece toward the doorclosure. Further, when the door is elevated preparatory to discharging the work from the machine, withdrawal of segment I46 by the door lowers the effective height of the end of the center-piece sufficiently to allow discharge of work thereover, without necessitating rotation of the center-piece to lower its effective end.

Although I have illustrated two drums, BI and 82, with a single .center segment 83,- and prefer to use this arrangement, it is to be understood that three or more drums may be associated with two or more segments without departing from the spirit of my, invention, and moreover, the intermediate drum or drums may have two open ends, so as to allow material to flow axially therebetween. Moreover, if desired in some instances, a single drum may be associated with a single segment for producing a tumbling apparatus of approximately one-half the capacity of that shown in the present case, and. the appended claims are intended to embrace my invention when the parts are related in this manner.

In order to preclude excessive angular rotation of centerpiece 83, and to automatically detercenterpiece is adapted to extend through the machine to the power unit (G). Rigidly mounted on shaft M7 is an upwardly projecting arm I48 adapted to be alternately'engaged by dogs I49 and I5I secured to spaced points on the periphery of the centerpiece by means of bolts I52 or the like. Arm I48 may assume the neutral position shown by full lines in Figure 6, or either of the positive positions I53 and I54 indicated by dotted lines inthe figure.

Should arm I48 be disposed in the position shown in Figure 6, application of power to shaft III] is prevented and rotation of the centerpiece prohibited. Should arm I48be disposed in either position I54 or I53, however, power may be applied to shaft III] and the centerpiece positively driven in either a forward or reversedirection respectively.

When it isdesired to effect rotation of the centerpiece, arm I48 is set in either position I53 or I54 by manual means to be escribed hereinafter. Upon application of power to shaft I III, the centerpiece is rotated until either dog I49 or I5I, as the case may be, engages arm I48 and 'actuates it into the neutral vertical position shown in full lines, at which time power is automatically shut oil? from shaft I III and the center.. piece is brought to rest. Upon being rotated, centerpiece 83 is thus automatically stopped in the'position desired and damage through excessive rotation is obviated.

Referring now to Figures-6, 8 and 9, extending inwardly from the front and rear cabinet walls escaping around the periphery of thesdrums into the machinery housed in, the remainder of the cabinet. The baffle plate assembly is also utilized for the purpose of retaining the workpieces in the correct path'of discharge upon unloading of the machine. The bafiie assembly depends be- .low the drums in the direction of shaft I" as shown at I62. As seen in Figure 8, bailie IGI is secured to the end of base plate 95 of the thrust roller assembly by any suitable means; as for example by brackets I60.

For the purpose of discharging work from the tumbling unit, the cabinet is preferably equipped with chutes I63 in a manner now to be described.

vided witha lug I66 designed to depend into the space between the above mentioned supports as shown clearly in Figure 6. By this construction chute I65 is prevented from movement toward the slab 4| by means of lug I66 and is prevented from side play by abutment of its ends against The chute, adjacent the centerpiece, is provided with recesses I61 adapted, when the end of the centerpiece 'is lowered, to accommodate projections I68 formed on theend of the centerpiece. In this manner a smooth discharge plane is formed and hindrance of egress of the a work from the machine caused by lack of alignment of the chute and the end-of the centerpiece is avoided.

A clearance I69 is provided between chute I63 and slab H to allow any abrasive, which escapes over the end of the centerpiece, to fall back into a collecting structure to be presently disclosed. To facilitate such recovery of misdirected abrasive, the lower edge of chute I63 is provided with flutes "I which are directed toward the center of the chute. The flutes at the bottom edge of the chute are in a plane lower than the top edge of slab M in order that inertia may not carry any of the abrasive, over the clearance gap I69.

While any suitable blast device may be used,

such as one or more compressed air blast nozzles,-

or any type of centrifugal wheel may be used with my apparatus, the following blast wheel is preferably used for projecting abrasive against the work. i

Referring now to'Figure 4, centrifugal discharge wheel (B) which is shown diagrammatically is' sure' to comprise the following elements. ,An internal sleeve I16disposed axially of the wheel is provided witha slot I11. Located within sleeve I18 is a paddle wheel I18 designed upon rotation to discharge abrasive through aperture I11, the abrasive being supplied to the sleeve at one end thereof. Abrasive so discharged is picked up by impeller blades I19 located radially outwardly of the slotted portion of the sleeve, which impart point.

In order to control and direct the blast, and to prevent rebound of abrasive from the tumbling unit back up to the wheel with consequent Wear and damage thereto, removable wear plates I and I8I are preferably provided at the front and rear respectively of the centrifugal wheel. Wear plate I80 is provided with a lug I82 projecting rearwardly therefrom and extending through a bracket I83 secured to the top of the cabinet (A) by bolts I84 or the like. Plate 180 is firmly held against bracket I83 by means of a wedge I85 accommodated within lug I82 and which slides against the back of bracket I83, thereby drawing'wea'r plate I80 close to the bracket and moval of the wear plate I80 for replacement because of wear, may be readily effected by simply removing wedge I85, withdrawing lug I82 from bracket. I83, and-lifting away the wear plate. i v

Wear plate I BI is removably assembled in a similar manner by means of 9. lug I86 and a "retaining the same in assembled relation. Re-

wedge- I01 to a bracket I88 which in turnflis .with a bent portion. I90.-.which is abutted by the rear end of the centerpiece when the same is in raised position. -Stop I89 is securedto a bracket I9I in any suitable manner which is in turn secured to the top of cabinet (A)" by means, of bolts I92'or the like.

Further protection against damage to the wheel by rebounding abrasive is afforded by wear plates I93 and I94, located at the sides of the discharge wheel (Figure 5). These wear plates are provided with flanges I 95 and I96 which are secured to a cover I91 extending above the centrifugal wheel opening in cabinet (A).

By means of the structure just defined, that portion of the discharge wheel extending within cabinet (A) is thoroughly protected against the' action of misdirected abrasive rebounding from the tumbling unit, and control of the direction taken by the fringe of the blast stream of abrasive is afforded,

Power for rotating the centrifugal wheel is sup-- plied-by means of a motor I98 mounted on top of the cabinet and connected to the centrifugal wheel axle shaft by means ofa belt I99.

With regard now to the manner of collecting the spent abrasive after its discharge into the tumbling unit upon the work therein contained, and referring particularly to Figures 6, 7 and 9, abrasive is drained from the drums 8I and 82 by virtue of the bowl-shaped inner contour thereof, and drain of the abrasive from the centerpiece is effected by means of, the sloping sides I 01 thereof. Abrasive so drained escapes from the tumbling unit through clearances I21 provided between the center-piece and each drum.

Extending inwardly and downwardly from flanges 200 of the front and rear cabinet walls, and of a width equal-to the width of main cabinet section 2,I is a trough 20I formed by members 202 and 203. The trough isprovided with front and rear door apertures 204 each sur-. rounded by adoor frame 205 which accommodates, bymeans of a hinge 206, a door 201 which comprises a bottom door plate 208; hinge ears 209; and a handle 2I0. Hinge 206 extends from ears 209 into enlarged apertures 2| I in the door frame and is therein adjusted by means of a set screw 2 I2, the door plate 208 in this fashion being adjustable with respect to a sealing gasket 2I3 fitting against the trough. Door 201 is retained in closed position by means of a bolt on latch 2I4, reciprocating in a guide 2I5 adjustable by means of a bolt 22I within a bracket 222 formed on the door frame, and pivoted at 2I6 to a handle 2 I1 which in turn is pivoted at '2I8 tov a. bracket 2 I9 formed on the door frame. I

In order to open either front or rear door 201 as the case'may be, handle 2 I 1 is rockedinwardly drawn from door plate 208 and the door being allowed to swing open. To close the door, handle 210 is grasped and drawn toward the outside edges is welded to vertical screen members 226 provided with flanges 221 which abut the trough 2M and are suitably secured thereto as by bolts 222. Disposed below and parallel to' screen 225, and terminating short of the trough 21H is a deflector 229 which at its sides is welded to vertical screens 226. edges of vertical screens 225 are brackets 236, which afford support for deflection plates 23!, the latter being provided with apertures 232.

As seen in Figure 6, the width of the assembly just described is somewhat greater than the distance between clearances I21 of the tumbling unit.

The assembly just described is for the purpose of, collecting and performing a preliminary screening operation upon the abrasive which escapes from the tumbling unit byway of clearances i211, and it functions in, the following manner. Abrasive which makes escape through clearances 622 is directed toward screen 225 from i the front and rear of the clearances by trough 25, and is guided toward the screen from the sides by baliie plates E68 and deflector plates 23E. Abrasive, upon reaching screen 225, passes therethrough and is guided toward the side of the trough by deflector plate 228 around the edge of which it escapes into the bottom of the trough.

Any pieces of wire, nails, chips from the work or other foreign matter escaping from the tumbling unit along with the abrasive, will be deflected by deflectors 23! toward the center of the inverted V ,screen 225, and upon striking screen 225 will be directed toward the door openings 2% in the side walls of the trough. Any abrasive falling upon deflectors 22.0 will be allowed to pass therethrcugh by means of apertures 232 with which the deflectors are provided. It will thus be appreciated that all material ,making exit from the tumbling unit by way of clearances i2? must either pass through screen 22am reach the bottom ofsthe trough or, upon failure to pass the screen, be directed to the door openings in the trough. Escape of abrasive to any other part of the machine than the screening device is preeluded by the battle and deflecting assemblies previously described.

Disposed in the space defined by screen 225 and the bottom 20:! of trough 2lll is a shaft 235, which extends through main cabinet 2! and auxiliary cabinets 22 and 23; Shaft 235 is journalled in seIf aligning bearings 236 secured to the outside walls of auxiliary cabinets 22 and 23. Bearings 236 are provided with spherical seats 231 in order that shaft 235 may be automatically adjusted in horizontal alignment regardless of casting inaccuracies of the housing members which support the bearings. .The bearings are'further provided withshields 238 fonpreventing abrasive or foreign:matter fr om enter n ;.lihe b aringsand causing damage thereto." Mounted on that portion of shaft 235 housed within the main cabinet member is a continuous seriesof helical screw segments 2 which when assembled com- Suitably secured to the upper.

2,108,210 about pivot 2l8, latch 2l4 being thereby withprise a screw conveyer extending for the entire width of the main housing 2|. The partition wall betweenmain cabinet 2| and auxiliary cabinet section 23 is provided adjacent the end of screw conveyer 24! with an aperture 242 which opens into a pit 243 formed in the bottom of auxiliary cabinet 23. a

As previously described, all abrasive passing through screen 225 is collected in the bottom 203 of trough- 201 and by means of the helical conveyer just described, such abrasive is advanced ing by means of elevator unit (F). Pit 243 forms the bottom of said elevator assembly, the housing of which is indicated in side elevation at 244 in Figure 1. Mounted upon shaft 235, within elevator housing 244, is a pulley 245 as seen in Figure 1. A similar pulley 246 is mounted in the top of the elevator housing in a manner to be directly disclosed. Extending between and about pulleys 245 and 246 is an endless belt conveyer 221 provided with buckets 248. Upon counter-clockwise rotation of pulleys 245 and 226, when viewed from the left of Figure 1, buckets 248 will-dip in succession into pit 243 and upon emerging will elevate uniform amounts of abrasive to the elevator head.

When the buckets pass over top pulley 246 (referring to Figure 17) during the operation just described, the centrifugal force imparted to the abrasive therein contained is sufficient to cause the abrasive to leave the buckets and be flung outwardly onto wear plate 249 which guides the elevated abrasive into a chute 25E. Wear plate 2431s designed to be removable in order that upon excessive wear caused by impingement of abrasive thereon, the plate may be readily replaced.

Fresh abrasive may be introduced into the ma= chine by means ofa hopper 252 (Figure 1) provided with a screen 253 and a hinged lid 25d, and communicating through an aperture 255 Hawaii .2? with pit 243. Conveyer belt 22?! is automatically kept under a predetermined tension throughout the life of the belt by means of a self-operating slack ad- -a hub 256 which by means of bearing 25? is freely rotatable upon a shaft 258 which extends through }\the walls of the elevator housing; Provided on the inner end of shaft 258, is a shield 259 for preventing ingress of abrasive or foreign anatter into bearing 251. On the outer end of shaft v258 and mounted for rotation therewith is a sheave 26I provided with a shield 262 for preventing ingress of foreign matter to bearing 251 from said outer end. Pulley 26l is provided with a peripheral channel 263 to accommodate a cable .264, one end of which is fastened by a bolt 265 to the rim of the pulley 26| and which, extending around the periphery of the pulley, depends from theother side thereof, and is fastened at its end to a weight 266 (Figure 17) Weight 266 is guid- ":fedin channel members 261 secured to the walls of the elevator housing.

Mounted on each end of shaft 258 outside of and consequently shaft 258, are constantly urged .ber 308-'provided with pawls' 308 adapted to en- .vided adjacent racks 212 on the elevator head the elevator housing is a pinion 211 designed for meshing engagement with a rack 212 spaced from the walls of the elevator housing by spacing members 213 and fastened together with the spacers to the housing walls by means of bolts 218 or the like. The end of shaft 258 nearest to pulley 261 is provided with a squared end 215 whereas the other end of the shaft receives a grease fitting 216 for lubrication of bearing 251. The operation of the slack take-up device is as follows: Weight 26 suspended by cable 264 will always impart a torque of constant magnitude to pulley 261 and thereby to shaft 258, resultin in a constant tendency for pinions 211 to roll along tracks 212. As seen in Figure 19, shaft 258 is always urged to rotate in a counter-clockwise direction and pinions 211 tend to roll upward along tracks 212 thereby elevating shaft 258. Such movement of shaft 258 is allowed with respect to the walls of the elevator housing by means of elongated apertures 211. Entrance of foreign substances into the elevator housing is prevented by means of straps 218 carried by shaft 258 and reciprocating in guides 218 formed in spacers 213. Squared ends 215 of shaft 258.allow application of a wrench for turning the shaft in order to facilitate manual adjustment of the tension in the belt conveyer. Ribs 281 are prosprocket 306 should be rotated in a clockwise direction, ratchet teeth 301 would merely cam past pawls 308 and no rotation of shaft 305 would eventuate. It is thus apparent that the pawl and ratchet arrangement just described forms a one-way driving connection between sprocket 306 and shaft 305. Power may be applied to rotate sprocket 306 in any suitable manner and in the present instance, power unit (G) is utilized inafter set forth.

Axially'. disposed about shaft 305 is a helical band 311 secured to the shaft by means of arms 312 mounted on collars 313 aflixed to the shaft. At spaced points about its periphery, band 311 is provided with buckets 314.

As previously set forth, abrasive entering cylinder 291 by way of chute 251, gravitates to the bottom of the cylinder. Upon rotation of shaft 305 and consequent rotation of helical band 31 I, buckets 314 dip successively into the abrasive resting in the bottom of the cylinder and, upon raising said abrasive to the top of the cylinder, allow the abrasive to filter downwardly again to the bottom while being washed by a counterstream of air in a manner to be presently described. The mass of abrasive is accordingly constantly advanced toward, and is eventually discharged into screen drum (J) by the screw action of helical band 31 I.

Referring for the present to cylindrical screen I unit (J) as disclosed in Figures 20 and 21, a drum upwardly, upper pulley 246 will be constantly housing 311 is seen to be mounted above and to urged upwardly with a force of uniform mag the rearof auxiliary cabinet 22. Housed within nltude 11nd belt Conveyor will b k pt t a drum 311 is a cylindrical screen 318 carried on u o a d C ta t te io hr u the life shaft 305 by means of a spider 318 attached to a e collar 320 mounted on shaft 305. The wire screen with reference now to Figures 20 and 3, the assembly comprises two drum ends 321 and 322; Spent abrasive, at the end transit thlll chute a sheet cylinder 323 provided with lateral slots 251 from elevator assembly (F), discharges into 324 and secured t t drum nd by angle pieces conveyer unit (H) which comprises a cylinder 325; a wire cylinder 325 upported by l t 281 and a helical screw 282. Cylinder 281 at one brackets 32 fastened to the end j and 1 1;- end opens into rotary screen unit (J) and at the end adjacent chute 251, opens into a chamber 283 formed above the rear part of auxiliary cabfor the purpose of lending rigidity to the structure.

'It will thus be apparent that as pinions 211,

cylinder 326 and supported by brackets 330 secured to the drum heads. Located within the met screen cylinder assembly is a hopper 331 accom- By means of opening 294 m the rear of the modating shaft 305 and terminating in a chute wall dividing auxiliary cabinet 23 from main outside f the drum housing I cabinet air be drawn from the main As seen in Figures 1 and 2, chute 332 opens into cabinet into the rear of the auxiliary cabinet, a bucket 333 having a handle 334 hung upon pass through a series of baffles 285, past a valve arms 335 secured'to'ang'les 336 mounted upon the 295 and mm through exhaust pipe Valve exterior'surface of the drum housing 311 for 296, mounted upon an axle 281, is actuated by the purpose of lending rigidity andstrength means of lei/er .reciprocatmg along m thereto. Bucket 333 is braced from the cabinet mounted auxmary cabinet 23 by means housing wall by a bracket 331 and at its lower end or lugs are secured t f by bolts receives a recovery drawer 338 below a screen 340. 302 or Guide provldqs stops for The operation of the screen unit just described lever when the latter assllmes its extreme is as follows: Abrasive discharged into the rotary gfi f i screen from the end of cylinder 281 gravitates assem y wi ecome ere na er man es.

Axially located within cylinder 281 and exll ggg gpg s fi gg ggg g g g gg ig L1? tendin throu h auxiliar cabinet 23 to seat in bearing 303' E througil screen cylinder unit through the screen into sheet cylinder 323 from (J) to seatin bearing 304, is a shaft 305. Mounted for free rotation upon the end of shaft 305 extending outwardly from auxiliary cabinet 23 is a sprocket wheel 306 providedwith a collar having ratchet teeth 301. Keyed rigidly to shaft 305 ajacent sprocket'306 is'a pawl carrying mem- Foreign matter such as wire, nails, small casting fragments and other adulterant entering the rotary screen with the abrasive are picked up by fins 328 in the screen cylinder, and upon being carried to the top of the cylinder are allowed to fall by gravity into hopper 331 and from thence age ratchet teeth 301. -'As seen"in:11 re 22,- when sprocket 306 is rotated in a counter-clock- I the coarse matter is retained by screw 341! wherewise direction, ratchet teeth 301 engage pawls as any entrained good abrasive trickles through 811115119313 is 9' d n a ounterscreen 340 into recovery drawer 338 from which to perform this function in a manner to be hereeral wire fins 328 extending inwardly from wire which escape is made into storage bin unit (K) clockwise direction. In the event, however; that are discharged into collection bucket 333, where it may be dumped periodically back into the machine to be removed by means of waste drawer 338. i

Thus it will be noted that onlypure and clean reclaimed abrasive is allowed to enter the storage bin for further use, all foreign substances berotary screen cylinder by means of an aperture 341 formed. in the wall separating the storage bin and the main cabinet. Air so drawn is upwardly deflected by a baiile 342 and passes around a sec- 'ond baflie 343, the rate of flow of air .being' con-' trolled bymeans of a valve 344 mounted on an axle 345 which is rotatably controlled by an arrangement to be presently described. B'afiies .342

'and 343 are for the primary purpose of deflecting abrasive falling into the storage bin away from the aperture 3 and thereby inhibiting egress of abrasive from the storage binby said aperture. Baiile 342 is braced against the outer wall of the storage bin by an arm 349, extending upward from which is a second arm 350 abutting the top of the storage bin and serving as a bearing support for axle345. It will be appreciated that air.

drawn from the interior of the cabinet will be a contaminated and impure, because of the dispersionof dust and other adulterants therethrough. Fresh air from the atmosphere may be drawn into drum housing 3" by way of a sector-shaped aperture 346 formed in the front of the drum housing and closed by means of a sector-shaped valve' 341 supported upon an axle 348. Control .of valves 344%;111 341 is effected by means of the following construction.

Secured in non-rotatable relation to shaft 345 is a lever 35" provided with a knob and is adapted to be actuated along a guide member 352 which provides stops for lever 35l at the extreme positions .thereof. Guide 352 is secured to the storage bin housing by means of lugs 353. Lever 35I is provided with an upper extension 354 which carries a p n 355 received in a slot 356 formed in a lever- 351 non-rotatably secured to shaft 348.

.The valve control de'saice operates in the following manner: Let us assume that lever 35! is moved to the left as viewed in Figure 20. Shaft 345 will then be rotated in a direction to close valve 344 toward its seat upon baiile 342. extension 354 will move to the right with pin 355 and the latter, by reciprocation in slot 356, will carrylever 351 to the right and cause shaft 346 ways flxed, the amount of fresh air increasing automatically as the amount of cabinet air decreases and vice ve'rsa. Intake ofair through the two valve ports just discussed and subsequent der 29L v opened to admit air from the main cabinet sec-.

Simultaneously,

I flow of the air stream to wash the abrasive is insured as a negative pressure or suctionalways exwithin exhaust through the conveyer. The silt and'dust laden air is exhausted by riieans of pipe (I) leaving the abrasive purified While the major part of such' washing action occurs within the conveyer cylinder, it is to be understood that such action also occurs within the rotaryscreen drum as abrasive is discharged therein in an agitated condition. g,

Under certain conditions, however, the current of air washing the abrasive may become undesi'rably strong and have a tendency to carry away particles of abrasive aswell as foreign matter into the exhaust pipe. With excessive suction in pipe (I) or whenthe very fine abrading material is used such undesirable conditions may prevail, and to remedy such evil effects, valve 296 and port 294, previously described, have been provided adjacent the abrasive intake and of cylin- Should the air stream flowing through cylinder 29! assume excessive velocity with the above described evil results, valve 296 maybe partially tion to flow throughaperture 294 and upwardly 35 to join the air stream from the cylinder as it leaves the cylinder and enters exhaust pipe (I). But as thevolume ofair entering pipe (I) is constant under a given condition of suction in the pipe, the volume of air entering the pipe from cylinder 25 is decreased when the valve' 296 is opened to admit flow of air there around and into pipe (I); Such reduction in the volume of air traveling through the cylinder 2!" lowers the velocity of the current, and in consequence, the miscarriage of abrasive particles along with the air current is obviated. Adjustment of valve 296 in correlation with adjustment of valves 344 and. 341 may thus be made to produce an air stream of desired velocity and having the proper components of atmospheric and cabinet air.

Abrasive discharged into storage bin unit (K) from the rotary screen falls to the bottom of the bin and is deflected by a plate 366 to one corner of the bin where is provided an aperture 36l opening into a valve 36.2 for metering abrasive into e evator unit (L). As seen in Figures 21, 23 and 2 abrasive passes from bin (K) through aper-" ture 36l into a drum 363 provided with a circular I aperture 364 in its bottom. Extending through drum 363 is a shaft 365 carrying outside of said drum a bucket 366 which in shape is similar to a segment of drum 363 and forms a close rotating fit thereabout. Bucket 366 is provided with a slot 361 adapted to register with aperture 364 upon adjustment of the valve bynneans hereinafter disclosed, mounted on the end of shaft 365 which extends outside of the machine housing. Upon registry "of slot 361 with aperture 364, abra sive is metered into a chute 368 which discharges the abrasive through a port 369 into elevator unit (L). Aperture 364 may be other'than circular if desired. It will be clear from an inspection of the drawings that storagerbin (K) and elevator unit (L) 75 

